The amount of e-Science software components deserves a sophisticated treatment. This article presents the MathWS, a broker, based on ontologies, to register, discover and execute mathematical web services. The Broker prototype uses innovative technologies such as OWL-S and MathML languages, and inference engines. Services can implement an algorithm or encapsulate an existent mathematical implementation. The broker structure, independent of applications that effectively execute algorithms, provides interoperability and reusability within e-science domains.